Fluid ejection devices typically include a number of fluid chambers which are in fluid communication with and receiving fluid from a fluid source, such as a fluid slot, via fluid passages. Typically, fluid chambers are one of two types, referred to generally as ejection chambers and non-ejection chambers. Ejection chambers, also referred to as “drop generators” or simply as “nozzles”, include a vaporization chamber having a nozzle or orifice and a drive bubble formation mechanism, such as a firing resistor, for example. When energized, the fluid ejector of a nozzle vaporizes fluid within the vaporization chamber to form a drive bubble which causes a drop of fluid to be ejected from the nozzle. Non-ejection chambers, also referred to as “recirculating pumps” or simply as “pumps”, also include a vaporization chamber and a fluid ejector, but do not include a nozzle. When energized, the fluid ejector of a pump also vaporizes fluid with the vaporization chamber to form a drive bubble, but since there is no nozzle, the drive bubble causes fluid to be “pumped” recirculated through associated fluid passages from the fluid slot to keep associated nozzles supplied with fresh fluid.